The invention relates to snowmobile maintenance and more particularly to the changing drive belts on snowmobiles and other machines using variable ratio drive belts. The recent popularity of snowmobiles for winter recreation has increased the number of both snowmobiles and snowmobilers. This has brought less experienced and less mechanically inclined people to the sport of snowmobiling. This surge in popularity, has brought one unintended consequence with the less experienced operators, more drive belts are becoming inoperative in the field.
The operation of a typical snowmobile involves the transmission of the power of the engine through a variable ratio drive belt and thence to the track. In the transmission of the power developed by the engine of a snowmobile, it is conventionally transmitted through a flexible, usually composite rubber, belt to a counter shaft and thence through a drive chain to the flexible track of the snowmobile that engages the snow or other surface that the snowmobile is riding upon.
Additionally, the belt drive uses variable diameter pulleys to provide a variable drive ratio to providing gear reduction to have increased power for starting and providing no gear reduction to allow a sufficiently high top speed and acceptable fuel economy. Usually, the variable ratio is accomplished using a pair of pulleys having a movable side or flange so that when the flanges of the pulley are separated, the effective diameter of the pulley is reduced, and when the flanges of the pulley are moved together, the pulley diameter is increased so that with the pair of pulleys working in concert, the drive ratio can be changed over a fairly wide range. This allows a snowmobile to have a reduction to a low drive ratio allowing the engine to develop sufficiently high revolutions to produce power to both start the snowmobile from a stopped position and negotiate a steep incline successfully and as the load decreases, and the speed increases, a lower drive ratio to provide the snowmobile with a sufficiently speed for economical cruising.
While the current drive belts are relatively long lived, the belts are a wear item and periodically wear out and must be replaced. The replacement of the drive belt involves a certain amount of strength, skill, and, all too frequently, frustration. Were the life of the drive belts predictable and a user judicious in performance of preventive maintenance, all of the belt changes could be performed in the comfort of an inside shop where a complete set of tools is available as part of scheduled maintenance. However, reality is that the life of a drive belt is unpredictable and may break or otherwise become unusable at any time, all too frequently, in the field miles away from a shelter or service facility. Upon this unpleasant occurrence, the user must replace the belt in the cold and the snow, often without adequate tools to assist him in performing the repairs. The unpleasant task is further complicated by the necessity of wearing gloves or mittens as protection from the cold weather.
The conventional method of changing belts involves manually forcing the sheaves of the drive pulley apart and holding the sheaves in this position while removing the old belt and then placing the new belt onto the pulleys while still holding the sheaves apart. Often, the user has difficulty separating the sheaves of the pulley and once the sheaves are separated, and the old belt removed, the sheaves are allowed to go back together and they must be again separated to install the new belt. Users, occasionally, will attempt to wedge a tool or other object between the sheaves of the pulley to keep the sheaves separated while changing belts. This procedure can work quite well in some circumstances, but, can lead to scoring the pulley sheave which significantly increases the wear and reduces the life of subsequent belts. The only solution being to replace a rather expensive pulley.
The invention disclosed herein is a tool which separates the sheaves of the drive pulley and holds the sheaves in a separated position from the end of the pulley thereby making it much easier and more convenient to change a drive belt while eliminating the scoring or defacing problems inherent with use of a tool to pry the sheaves apart directly. The invention acts only on the shroud of the pulley and not on the faces of the pulley.
When changing a drive belt on a snowmobile or the like, if the old drive belt has not broken, it must first be removed by forcing the flanges of the one pulley apart to reduce their effective diameter so that both the drive pulley and the driven pulley are at a minimum effective diameter so as the drive belt can be removed. The flanges of the drive pulley are typically held together by springs and the tension of these springs must be overcome and the flanges held apart to remove the drive belt. If the flanges are then allowed to come back together, they must be reopened to allow the installation of a new belt. While this task is difficult to do in a warm shop with the snowmobile on a bench, it can become nearly impossible in the cold with the snowmobile nestled down in the snow. This is particularly true where the user must wear gloves or mitts as protection from the cold.
The invention disclosed herein is a tool that allows a user to easily and readily urge the flanges of a drive pulley apart and hold the flanges apart while removing the defective drive belt and replacing the drive belt with a new drive belt. More particularly, the invention includes a small circular adapter plate that is attached to the terminal end of the shaft carrying the drive pulley and a pivoting tool having a yoke that engages the adapter plate and locates the tool so as that the user can actuate the handle to move the drive pulley flanges apart and hold the pulley flanges apart to change the drive belt and after replacing the drive belt with a new drive belt, release the handle, and thereby allow the pulley flanges to be urged together by the spring and return to their resting position.